Inverter starting circuit



y 13, 1952 B. L. SCHERER 2,596,606

INVERTER STARTING CIRCUIT Filed April 19, 1951 j; ifia 20 L 22 no I i i POWER I mvERTER SUPPLY 25.

/0 fig 7 Z2 nc.

RowER INVERTER SUPPLY INVENTOR.

-EEENAK'D L, SCHERER ATTORNEY Patented May 13, 1952 nther? n en ion e a es to eli rfireu p nverte s nd re ets m re P rt cu a l t means. e

ei ZlYT e' P s1 a de etr n ii erber t igh directcurre nt voltages;

'The' changing of direct current into alternating eurrent is known asinversion and, the eieo trcnic tuhe'andits related circuit elements used forthis' purpose are '1 :novv1'n. 'asir'iver ters Vaeu u'thftub oscillators can be used forthis function biit" are" used, prir'naril'y in 'low -current'circuits where sinusoidal waveforms, high requenc es ora combination of hothare required.

For hig'nurr'em, dependable and highly I ear ciefit power 1 inversion gas filledf' tubes having characteristically low internal "resistance "and practically current arc-drop" are ideal, "Consequnny; 'mos'timv'erten; ern'ploy either" the thyraden type of mammary re type/tube. Such circuits,'"however', are relatively difii c'ulttp start oscillating at] high values or; impressed direct current voltage. I f' thevolta'ge can be reduced for a short period theinv'erter will start quite readily: a M, I it a "'Itfis therefore an object of the invention to provide a starting "Circuit'which in combination with an electronic inverter will enable" "said in verter to s'tarteas'ilv even when the voltage of the direct current source isreiativelyhighl' It is'an'other object of "the inventio'n'to provide a starting' cireuit which wmena iean electronic inverter "to 'startreadily and where: saidfstar'ting dirouit actisf'to plate a temporary load on said mvmen ane to remove said lead as soon" as the i v ter. e in o per te "Still" another "olo 'je"c:ti's to provide a starting circuit for an inverterwherein the direct current voltage to" the inverter is "momentarily reduced by the insertion of a resistance'in series "with one of the direct current" power leads.

Theahove and "other objects of the invention Inay he rnore readily understood from the foldetailed description particularly? when taken in eolnsideration with the accompanying drawing wherein satis faoto ry embodiments" of 1 en ive h 'wn weve .51 t be understoodthat"thefihventionis not limited to the; details fdis'clo'sed but includes all such' varia tions and modifications" as: 'falltwith in the spirit offtheinvention and 'thescope of the appended c aims}. 4 V

In thedrawings;

Figi'l isjfaf schematic circuit diagram of one e bodi rnentbflthle invention; and" 2' i'sfa schematic: cireuit diagram of an: m o men e in ent on wh ein.

res s anee s essrtedi i s w h. P F lead ,v r a. M it is agreed that inverters are well known in the art sham-titer, as'mt" starting c'irfit is notlirrlite'd to any'particular type'oflelectronie inverter, such an inverter is shown'in'blook 'f Tin ifibothfigruigs'm .i. r t ,i "Referring now to Fig. 1, aninverter Illis connected to its source of'direct our nt: Sum- 11 11 by rnean's of 'cenn'e c; ens" l2 and l3.""Coiinection I'ZL iS'cdnneotedi to 'a positiveitrminal l4 of the ower supply it and. connection 1351 unn e e to'ane'gative terminalf l5.' In" a "conventional inverter; the ot er end of c nn'es tionil, z is 0on1- n'eeted "to the een ter'tapof 'a 'pla'te'tran sfdr er and. negative connection I3, is cor merited to the cathodes of the'inve'rter tubes; "Aoapacitor [6 has on'efterininal connected, to the positive terminfl'f'mfoffthe powefsupply'll, the Other'sid'e of capacitor l6 being' c'onneoted to one end of a winding I! of an electromagnetic relay [8 The otherendofj the winding l'lfis connected tothe negative connection). Thus; the'capacitor t6 and winding l'fiare'conjn'ectedin series across the direct 'currentsuppiy '1. I i, ii. i. .r. VH1

The electromagnetic relay [8 has a pair of switching contacts including" a movable contact '9. an a ed acti fl? im va 0111 tact l5 is coniiecftedby' a lead 2.! to an output angina. fi ifaiid the fixedfeontact 2 6' eon i et l by ea h s a ad; r sist? a; 24 a nd. ut ut erm na 25 h un t on n o he circuit may ereadi v understood. Assunrie'the power supply H tob e turned ofi' and the inverter I0, as aresult, nonoperating'. Then at the instantthe power supply "II is energized a direct current potential appears across'theterrninal's l4 and [5. This potential causes a current to flow from positive terminal l4, through the capacitor 16 and the winding to the negative terminal l5. "At the instant the power supply H "is' energized; -"the entire "voltage across theterminal's Ii-and I5 I appears across the winding 'l'i o'fthe eleetromagnetic relay l8.

The current flowing through the winding causes a magnetic'field' to'be setup suf i ic'ie'nt tsets the movable contact I9 and thus 'plaoethe' resist ance 24 as a load "across the outputterrninaleu and" 25 of the inverter l0. Withjthe load srssfih na s h nv rter/ 0 s. a o W mwe s ha u k iaf' qal 9'; prese As, heretof e mentioned j lwqesiifii-i verters are particularly hard to start especially at relatively high direct current voltages.

A short time after the power H is energized, the capacitor l becomes charged and eventually all of the voltage appears across the capacitor it, current then ceases to flow and the relay i8 is tie-energized. The movable contact IE will then open and return to its normal position and hence the load resistance 24 is no longer across the output terminals 22 and 25.

An embodiment of the invention which illustrates the principle of momentarily reducing the direct current voltage applied to the inverter is shown in Fig. 2. In this figure, like parts are shown by like numbers and as in the instance of the embodiment of Fig. 1, a capacitor 16 in series with the winding 11 of an electro-magnetic relay I8 is connected across the output terminals 14 and i5 of a source of direct current power H. The power supply I provides the source of power for the inverter [0. In the embodiment of Fi 2, the movable contact [9 is normally closed against the fixed contact 20 so that normally the positive terminal I4 is connected through lead l2, movable contact 19, fixed contact 20 and lead 26 to an input terminal 21 of the inverter Hi. The negative terminal i5 is connected to another in put terminal 28 by the connection I3.

A resistance 29 is connected across the movable contact I9 and the fixed contact 20 of the relay l8. Thus, when these contacts are open the positive terminal I 4 is connected through lead 12, through the resistance 29 to the input terminal 21. When this resistance 29 is in the circuit there is, of course, a substantial voltage drop across the resistance and the voltage across the input terminals 21 and 2B is reduced to allow the inverter in to start easily.

Upon energizing the power supply, all of the voltage across the terminals 14 and I5 appears across the winding IT. The relay is energized and movable contact i9 is drawn away from contact 20 thus putting the resistance 29 in series with the power lead from the positive terminal H to the input terminal 21. input voltage across the terminals 21 and 28 is reduced and the inverter [0 starts. A short time later the capacitor I6 is fully charged and current ceases to flow through the winding IT. The relay I8 is then de-energized, contacts I9 and 20 are again closed to short circuit the resistance 29 and to restore the full supply voltage to the input terminals 21 and 28.

In both the circuits of Fig. 1 and Fig. 2, the length of time the relay [8 is operative is dependent upon the value of the capacitor and the direct current resistance of the winding IT. The longer the time constant of the circuit the longer it will take the capacitor IE to charge and hence the longer the relay I8 will be operative. As it is thus very easy to vary the time constant, a time interval suificient to allow the inverter to start can readily be provided.

Having thus set forth the nature of my invention, what I claim is:

1. In combination with an electronic inverter being supplied from a source of direct current potential, means for readily starting said inverter by momentarily reducing the magnitude of said direct current potential, said means including switching means adapted to be operative upon the surge of current which occurs when said source of potential is energized and rendered non-operative when said surge has passed, resistance means associated with said switching As stated above, the

means whereby when said switching means is operative said resistance means loads said source of direct current potential to reduce the magnitude of the potential supplied the inverter to enable said inverter to start readily.

2. In combination with an electronic inverter being supplied from a source of direct current potential, means for readily starting said inverter by a temporary load, said means including switching means adapted to be operative upon the surge of current which occurs when said source of potential is energized and rendered non-operative when said surge has passed, resistance means associated with said switchin means whereby when said switching means is operative said resistance means serves as a load for said inverter to enable said inverter to start readily.

3. In combination with an electronic inverter being supplied from a source of direct current potential, means for readily starting said inverter by temporarily loading said inverter, said means including an electro-magnetic relay having a winding and a pair of contacts, a capacitor serially connected with said winding, the series combination of said winding and said capacitor being connected across the source of direct current potential, a temporary load for said inverter, an electrical connection of said temporary load and said contacts whereby when said source of direct current potential is energized current flows through said capacitor and said winding to operate said relay and place said temporary load across the inverter to enable said inverter to start readily and further whereby when said capacitor is fully charged the relay is de-energized and the temporary load is removed.

4. In combination with an electronic inverter supplied from a source of direct current potential, means for readily starting said inverter by temporarily loading said inverter, said means including an electro-magnetic relay having a winding and a pair of contacts, said contacts being open when said relay is non-energized and closed when energized, a capacitor serially connected with said winding, the serie combination of said winding and said capacitor being connected across the source of direct current potential, and a temporary load for said inverter, said load being connected in series with said pair oi contacts whereby when said source of direct current potential is energized current flows through said capacitor and said winding to operate said relay and close said contacts to put said temporary load across said circuit to enable said inverter to start readily and whereby when said capacitor is fully charged current ceases to flow. the relay is de-energized and said contacts open to remove said temporary load.

5. In combination with an electronic inverter supplied from a source of direct current potential, means for readily starting said inverter by momentarily reducing the magnitude 01' said potential, said means including an electro-magnetic relay having a winding and'a pair of contacts, said contacts being closed when said relay is non-energized and open when energized, a capacitor serially connected with said winding, the series combination 01 said winding and said capacitor being connected across th source of direct current potential, and a resistance serially connected between said source of potential and the inverter being supplied therefrom, said resistance being normally short circuited by being also connected directly across said normally closed contacts whereby when said source of di- 5 rect current potential is energized current flows REFERENCES CITED through said capacitor and Said winding to Opel The following references are of record in the ate said relay and to open said contacts to refile of this patent:

move said short circuit from said resistance and thereby lower the direct current potential ap- 5 UNITED STATES PATENTS plied to said inverter and whereby when said ca- Number Name Date pacitor is fully charged current ceases to flow, 1,759,745 Grimditch May 20, 1930 the relay is de-energized and said contacts close 1,760,580 Brown May 27, 1930 to short circuit said resistance.

BERNARD L. SCHERER. 10 

